Method and system for treating a hard mask to improve etch characteristics

ABSTRACT

During pattern transfer to a film stack, the hard mask layer, such as a tunable etch resistant antireflective coating (TERA), is consumed when etching the underling layer(s), leading to reduced etch performance and potential damage to the underlying layer(s), such as lack of profile control. A method of and system for preparing a structure on a substrate is described comprising: preparing a film stack comprising a thin film, a hard mask formed on the thin film, and a layer of light-sensitive material formed on the hardmask; forming a pattern in the layer of light-sensitive material; transferring the pattern to the hard mask; removing the layer of light-sensitive material; treating the surface layer of the hard mask in order to modify the surface; and transferring the pattern to the thin film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of treating a hard mask toimprove etch characteristics and, more particularly, to a method oftreating a hard mask in order to modify the surface layer of the hardmask.

2. Description of Related Art

In material processing methodologies, pattern etching includes theapplication of a patterned mask of radiation-sensitive material, such asphotoresist, to a thin film on an upper surface of a substrate, andtransferring the mask pattern to the underlying thin film by etching.The patterning of the radiation-sensitive material generally involvescoating an upper surface of the substrate with a thin film ofradiation-sensitive material and then exposing the thin film ofradiation-sensitive material to a radiation source through a reticle(and associated optics) using, for example, a photolithography system.Then a developing process is performed, during which the removal of theirradiated regions of the radiation-sensitive material occurs (as in thecase of positive photoresist), or the removal of non-irradiated regionsoccurs (as in the case of negative resist) using a base developingsolution, or solvent. The remaining radiation-sensitive material exposesthe underlying substrate surface in a pattern that is ready to be etchedinto the surface. Photolithographic systems for performing theabove-described material processing methodologies have become a mainstayof semiconductor device patterning for the last three decades, and areexpected to continue in that role down to 65 nm resolution, and less.

The resolution (r_(o)) of a photolithographic system determines theminimum size of devices that can be made using the system. Having agiven lithographic constant k₁, the resolution is given by the equationr _(o) =k ₁ λ/NA,  (1)

-   -   where λ is the operational wavelength, and NA is the numerical        aperture given by the equation        NA=n·sin θ_(o).  (2)

Angle θ_(o) is the angular semi-aperture of the system, and n is theindex of refraction of the material filling the space between the systemand the substrate to be patterned.

Therefore, current lithographic trends involve increasing the numericalaperture (NA) in order to print smaller and smaller structures. However,although the increased NA permits greater resolution, the depth of focusfor the images projected into the light-sensitive material is reduced,leading to thinner mask layers. As the light-sensitive layer thicknessdecreases, the patterned light-sensitive layer becomes less effective asa mask for pattern etching, i.e., most of the (light-sensitive) masklayer is consumed during etching. Without a dramatic improvement in etchselectivity, single layer masks have become deficient in providing thenecessary lithographic and etch characteristics suitable for highresolution lithography.

An additional shortcoming of single layer masks is the control ofcritical dimension (CD). Substrate reflections at ultraviolet (UV) anddeep ultraviolet (DUV) wavelengths are known to cause standing waves inthe light-sensitive layer due to thin film interference. Thisinterference manifests as periodic variations in light intensity in thelight-sensitive layer during exposure resulting in vertically spacedstriations in the light-sensitive layer and loss of CD.

In order to counter the effects of standing waves in the light-sensitivelayer as well as provide a thicker mask for subsequent pattern etchtransfer, a bilayer or multilayer mask can be formed that incorporates abottom anti-reflective coating (BARC). The BARC layer includes a thinabsorbing film to reduce thin film interference; however, the BARC layercan still suffer from several limitations including poor thicknessuniformity due in part to spin-on deposition techniques.

A hard mask may also be used to provide improved maintenance of criticaldimensions. The hard mask may be a vapor deposited thin film providedunder the light sensitive layer to provide better etch selectivity thanthe light sensitive layer alone. This etch selectivity of the hard maskmaterial permits use of a thinner mask that allows greater resolutionwhile also allowing a deeper etch process. The present inventors haverecognized, however, that the use of conventional hard masks havelimited etch selectivity and resilience to etch processes that willlimit their use in future generation devices with even smallerstructures.

SUMMARY OF THE INVENTION

One aspect of the present invention is to reduce or eliminate any or allof the above-described problems.

Another object of the present invention is to provide a method oftreating a hard mask to improve etch characteristics.

Yet another aspect of the present invention is to provide a method oftreating an organosilicate layer.

Yet another aspect of the present invention is to provide a method oftreating a tunable etch resistant anti-reflective (TERA) coating.

These and/or other aspects of the invention may be provided by a methodof preparing a structure on a substrate including preparing a film stackhaving a thin film, a hard mask formed on the thin film, and a layer oflight-sensitive material formed on the hard mask; forming a pattern inthe layer of light-sensitive material; transferring the pattern to thehard mask; removing said layer of light-sensitive material; treating thesurface layer of the hard mask in order to modify the surface layer; andtransferring the pattern to the thin film.

According to yet another aspect, a chemically altered hard mask includesa hard mask layer and a chemically altered surface layer of the hardmask layer.

According to yet another aspect, a plasma processing system for treatinga hard mask used for etching a feature in a thin film on a substrateincludes: a process chamber; a substrate holder coupled to the processchamber and configured to support the substrate; means for introducing atreating gas; means for forming a plasma; and a controller coupled tothe means for introducing the treating gas and the means for forming theplasma, and configured to execute a process recipe utilizing the plasmato chemically alter the surface layer of the hard mask.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A, 1B, and 1C show another schematic representation of a typicalprocedure for pattern etching a thin film;

FIGS. 2A, 2B, and 2C illustrate a schematic representation of a methodfor treating a hard mask according to an embodiment of the presentinvention;

FIG. 3 shows a method for treating a hard mask according to anembodiment of the present invention;

FIGS. 4A, 4B, and 4C illustrate a schematic representation of a methodfor treating a hard mask according to another embodiment of the presentinvention;

FIG. 5 shows a simplified schematic diagram of a plasma processingsystem according to an embodiment of the present invention;

FIG. 6 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention;

FIG. 7 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention;

FIG. 8 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention; and

FIG. 9 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

As described earlier, the use of a hard mask has been adopted tocomplement the lithographic structure, and can be utilized inapplications where the specifications for critical dimensions arestringent. One variety of hard masks can be broadly classified asorganosilicate materials, and one such organosilicate material is atunable etch resistant anti-reflective (TERA) coating. These TERAcoatings can be produced having a tunable index of refraction andextinction coefficient which can be optionally graded along the filmthickness to match the optical properties of the substrate with theimaging light-sensitive layer; see U.S. Pat. No. 6,316,167, assigned toInternational Business Machines Corporation. As described in thispatent, TERA films are used in lithographic structures for front end ofline (FEOL) operations, such as gate formation, where control of thecritical dimension is very important. In these applications, TERAcoatings provide substantial improvement to the lithographic structurefor forming gate devices at the 65 nm device node and smaller.

The present inventors have discovered, however, that conventional hardmask films such as TERA coatings can be damaged during processing steps.As noted above, in material processing methodologies, pattern etchingutilizing such a lithographic structure generally includes theapplication of a thin layer of light-sensitive material, such asphotoresist, to an upper surface of a substrate, that is subsequentlypatterned in order to provide a mask for transferring this pattern tothe underlying hard mask during etching. Once the pattern is transferredto the hard mask, the layer of light-sensitive material is typicallyremoved using an oxygenated plasma, and the pattern formed in the hardmask can be transferred to the underlying thin film. The presentinventors have recognized that the conventional hard mask has an etchselectivity inherent to the material of the hard mask and which limitsetch depth for a given thickness of hard mask. The present inventorshave discovered that treatment of the hard mask material according tothe present invention provides improved characteristics for the hardmask.

FIGS. 1A-1C show a conventional etching process to which a hard masklayer treatment process of the present invention can be applied. Asshown in FIG. 1A, a bilayer mask 6 including light-sensitive layer 3with pattern 2 formed using conventional lithographic techniques isformed on a hard mask layer 7, which is formed on a thin film 4 on topof a substrate 5. As seen in FIG. 1B, the hard mask 7 can be utilized asa mask for etching the thin film 4, wherein the mask pattern 2 in thelight-sensitive layer 3 is transferred to the hard mask 7 using aseparate etch step preceding the main etch step for the thin film 4. Themain etch step to the film 4 is shown in FIG. 1C.

In one embodiment of the present invention, a process gas including anoxygen-containing gas is introduced to a plasma processing system inorder to form an oxygen plasma. Thereafter, a substrate having apatterned hard mask, such as an organosilicate layer, is exposed to theoxygen plasma in order treat the exposed surface layer of the hard mask.In an alternate embodiment, the treatment of the hard mask is performedduring the removal of the light-sensitive layer from the substrate. Inyet another alternate embodiment, the treating of the hard mask isperformed following the removal of the light-sensitive layer. Thepresent inventors have discovered that treating the hard mask in thisway improves the etch characteristics of the hard mask.

Specifically, the treated hard mask has an oxygenized hardened surfacethat has an improved etch selectivity over the untreated hard mask. Thisallows a deeper etch process to be performed for a given hard maskthickness. Moreover, the treated hard mask of the present inventionprovides greater control of critical dimension. As to this criticaldimension improvement, the present inventors have recognized that evenif a conventional untreated hard mask provides the appropriate thicknessto perform a given etch process, poor resiliency of the hard mask at thepattern edges leads to break down of these edges during etching and,consequently, relatively poor control of the critical dimension ofdevice features. Treating the hard mask according to the presentinvention is believed to make the pattern edges of the hard mask moreresilient to semiconductor processes thereby allowing better control ofcritical dimension.

In another embodiment, referring now to FIGS. 2A through 2C, and FIG. 3,a method of preparing a feature in a film stack is described. FIGS.2A-2C show the film stack structure, while FIG. 3 describes processsteps 310-380 performed on the film stack of FIGS. 2A-2C. As depicted inFIG. 2A and FIG. 3, a film stack 200 is prepared on a substrate 230,wherein the film stack 200 includes a thin film 225 formed on substrate230 in step 310, a hard mask 220 formed on the thin film 225 in step320, and a layer of light-sensitive material 210 formed on the hard mask220 in step 330. The thin film 225 can include at least one ofmono-crystalline silicon, poly-silicon, doped silicon, silicon nitride,silicon dioxide, a low dielectric constant (low-k) dielectric, etc. Thethin film can be deposited using at least one of chemical vapordeposition (CVD), or spin-on techniques, each of which is well known tothose skilled in the art.

The hard mask 220 can include an organosilicate layer. For example, thehard mask can include a tunable etch resistant anti-reflective (TERA)coating.

The TERA coating includes a structural formula R:C:H:X, wherein R isselected from the group consisting of Si, Ge, B, Sn, Fe, Ti, andcombinations thereof, and wherein X is not present or is selected fromthe group consisting of one or more of O, N, S, and F. The TERA coatingcan be fabricated to demonstrate an optical range for index ofrefraction of approximately 1.40<n<2.60, and for extinction coefficientof approximately 0.01<k<0.78. Alternately, at least one of the index ofrefraction and the extinction can be graded (or varied) along athickness of the TERA coating. Additional details are provided in U.S.Pat. No. 6,316,167, entitled “Tunable vapor deposited materials asantireflective coatings, hardmasks and as combined antireflectivecoating/hardmasks and methods of fabrication thereof and applicationthereof, assigned to International Business Machines Corporation; theentire contents of which are incorporated herein in their entirety.Furthermore, the TERA coating can be formed using PECVD, as described ingreater detail in pending U.S. patent application Ser. No. 10/644,958,entitled “Method and apparatus for depositing materials with tunableoptical properties and etching characteristics”, filed on Aug. 21, 2003;the entire contents of which are incorporated herein in their entirety.The optical properties of the TERA coating, such as the index ofrefraction, can be selected so as to substantially match the opticalproperties of the underlying layer, or layers. For example, underlyinglayers such as non-porous dielectric films can require achieving anindex of refraction in the range of 1.4<n<2.6; and underlying layerssuch as porous dielectric films can require achieving an index ofrefraction in the range of 1.2<n<2.6.

Additionally, for example, the layer of light-sensitive material 210 caninclude photoresist. For example, the layer (or layers) oflight-sensitive material 210 can be formed using a track system. Thetrack system can be configured for processing 248 nm resists, 193 nmresists, 157 nm resists, EUV resists, (top/bottom) anti-reflectivecoatings (TARC/BARC), and top coats. For example, the track system caninclude a Clean Track ACT 8, or ACT 12 resist coating and developingsystem commercially available from Tokyo Electron Limited (TEL). Othersystems and methods for forming a photoresist film on a substrate arewell known to those skilled in the art of spin-on resist technology.

Once the layer of light-sensitive material 210 is formed on film stack200, it can be patterned with a pattern using micro-lithography in step340, followed by the removal of the irradiated regions of thelight-sensitive material (as in the case of positive photoresist), ornon-irradiated regions (as in the case of negative resist) using adeveloping solvent. The micro-lithography system can include anysuitable conventional stepping lithographic system, or scanninglithographic system. As shown in FIG. 2B, the pattern can be transferredto the hard mask 220 in step 350 using, for example, dry plasma etching.The dry plasma etch process can include a plasma chemistry containing atleast one of the species selected from the group consisting of oxygen,fluorine, chlorine, bromine, hydrogen, and combinations thereof.Alternatively, the plasma chemistry can further include nitrogen or aninert gas, such as a Noble gas (i.e., helium, neon, argon, xenon,krypton, radon). Still alternatively, the plasma chemistry is chosen toexhibit high etch selectivity between the etch rate of the hard mask andthe etch rate of the overlying patterned layer of light-sensitivematerial. Still alternatively, the plasma chemistry is chosen to exhibithigh etch selectivity between the etch rate of the TERA coating and theetch rate of the underlying thin film. Once the pattern is transferredto the hard mask 220, the patterned hard mask can be utilized totransfer the pattern to the underlying thin film.

In step 360, the remaining light-sensitive material 210 is then removedusing an oxygen-containing plasma. For example, the oxygen-containingplasma can be formed by introducing oxygen (O₂). In step 370, thesurface of the exposed hard mask is treated using an oxygen-containingplasma in order to form a chemically altered layer 250 in the hard mask220. In one embodiment, the layer of light-sensitive material isremoved, and the surface layer of the hard mask is treated concurrently.Alternately, the surface layer of the hard mask is treated following theremoval of the layer of light-sensitive material. For example, asdescribed above, a treatment process for removing a light-sensitivematerial and treating a hard mask can include exposing the layers to anoxygen-containing plasma for 20 to 1400 seconds at a substrate holdertemperature ranging from 20 C to 400 C. For example, a substrate with ahard mask having a thickness of approximately 1000 Å can be exposed toan oxygen plasma for 60 seconds at a substrate holder temperature of 250C in order to remove the remaining layer of light-sensitive material,followed by exposure to the oxygen plasma for 120 seconds (i.e., 200%“over-treatment”) at a substrate holder temperature of 250 C in order toform a chemically altered layer having a thickness ranging from 10 Å(i.e., partially treated) to 1000 Å (i.e., fully treated). Additionally,for instance, if the substrate holder temperature is reduced (e.g., from250 C), then the exposure time can be increased to accommodate theslower process. Additionally, for example, the light-sensitive materialcan be exposed to an oxygen-containing plasma for 10 seconds to 200seconds at a substrate holder temperature of 20 C to 400 C, and the hardmask layer can be exposed to an oxygen-containing plasma for 10 secondsto 1200 seconds at a substrate holder temperature of 20 C to 400 C.

Thereafter, in step 380, the pattern in the hard mask is transferred tothe underlying thin film, using, for example, dry plasma etching. Forinstance, when etching silicon films, the etch gas composition generallyincludes at least one of SF₆, HBr, Cl₂, etc. Additionally, for example,when etching oxide dielectric films such as silicon oxide, silicondioxide, etc., or when etching inorganic low-k dielectric films such ascarbon doped silicon oxide materials, the etch gas composition generallyincludes a fluorocarbon-based chemistry such as at least one of C₄F₈,C₅F₈, C₃F₆, C₄F₆, CF₄, etc., and at least one of an inert gas, oxygen,or CO. Additionally, for example, when etching organic low-k dielectricfilms, the etch gas composition may include at least one of afluorocarbon gas, a nitrogen-containing gas, a hydrogen-containing gas,or an oxygen-containing gas. The techniques for selectively etching adielectric film, such as those described earlier, are well known tothose skilled in the art of dielectric etch processes.

In yet another embodiment of the invention, referring now to FIGS. 4Athrough 4C, a method of preparing a feature in a film stack isdescribed. As depicted in FIG. 4A, a film stack 400 is prepared on asubstrate 440, wherein the film stack 400 includes a poly-silicon film435 formed on substrate 440, a doped silicon film 430 formed on thepoly-silicon film 435, a silicon nitride film 425 formed on the dopedsilicon film 430, a hard mask 420 formed on the silicon nitride film425, and a layer of light-sensitive material 410 formed on the hard mask420. Once a pattern is formed in the layer of light-sensitive material410, the pattern is transferred to the hard mask, and to the underlyingsilicon nitride film 425. Thereafter, the layer of light-sensitivematerial 410 is removed, and the surface layer of the hard mask 420 istreated in order to form a chemically altered layer 450.

The etching process(es), the ashing process, and the treating processrelating to a hard mask treating process of the present invention can beperformed in a plasma processing system. The processes can be performedin the same plasma processing system, or in separate plasma processingsystems.

For example, FIG. 5 presents an exemplary plasma processing system 1that may be used to implement a process of the present invention. Asseen in this Figure, the plasma processing system 1 includes a plasmaprocessing chamber 10, a diagnostic system 12 coupled to the plasmaprocessing chamber 10, and a controller 14 coupled to the diagnosticsystem 12 and the plasma processing chamber 10. The controller 14 isconfigured to execute a process recipe including at least one of anetching process, and an ashing process. Additionally, controller 14 isconfigured to receive at least one endpoint signal from the diagnosticsystem 12 and to post-process the at least one endpoint signal in orderto accurately determine an endpoint for the process. In the illustratedembodiment, plasma processing system 1, depicted in FIG. 5, utilizes aplasma for material processing. Plasma processing system 1 can includean etch chamber, or an ash chamber.

According to the embodiment depicted in FIG. 6, a plasma processingsystem 1 a used in accordance with the present invention can includeplasma processing chamber 10, substrate holder 20, upon which asubstrate 25 to be processed is affixed, and vacuum pumping system 30.Substrate 25 can be, for example, a semiconductor substrate, a wafer ora liquid crystal display. Plasma processing chamber 10 can be, forexample, configured to facilitate the generation of plasma in processingregion 15 adjacent a surface of substrate 25. An ionizable gas ormixture of gases is introduced via a gas injection system (such as a gasinjection pipe, or gas injection showerhead) and the process pressure isadjusted. For example, a control mechanism (not shown) can be used tothrottle the vacuum pumping system 30. Plasma can be utilized to creatematerials specific to a pre-determined materials process, and/or to aidthe removal of material from the exposed surfaces of substrate 25. Theplasma processing system 1 a can be configured to process 200 mmsubstrates, 300 mm substrates, or larger.

Substrate 25 can be, for example, affixed to the substrate holder 20 viaan electrostatic clamping system. Furthermore, substrate holder 20 can,for example, further include a cooling system including a re-circulatingcoolant flow that receives heat from substrate holder 20 and transfersheat to a heat exchanger system (not shown), or when heating, transfersheat from the heat exchanger system. Moreover, gas can, for example, bedelivered to the back-side of substrate 25 via a backside gas system toimprove the gas-gap thermal conductance between substrate 25 andsubstrate holder 20. Such a system can be utilized when temperaturecontrol of the substrate is required at elevated or reducedtemperatures. For example, the backside gas system can include atwo-zone gas distribution system, wherein the helium gas gap pressurecan be independently varied between the center and the edge of substrate25. In other embodiments, heating/cooling elements, such as resistiveheating elements, or thermoelectric heaters/coolers can be included inthe substrate holder 20, as well as the chamber wall of the plasmaprocessing chamber 10 and any other component within the plasmaprocessing system 1 a.

In the embodiment shown in FIG. 6, substrate holder 20 can include anelectrode through which RF power is coupled to the processing plasma inprocess space 15. For example, substrate holder 20 can be electricallybiased at a RF voltage via the transmission of RF power from a RFgenerator 40 through an impedance match network 50 to substrate holder20. The RF bias can serve to heat electrons to form and maintain plasma.In this configuration, the system can operate as a reactive ion etch(RIE) reactor, wherein the chamber and an upper gas injection electrodeserve as ground surfaces. A typical frequency for the RF bias can rangefrom 0.1 MHz to 100 MHz. RF systems for plasma processing are well knownto those skilled in the art.

Alternately, RF power is applied to the substrate holder electrode atmultiple frequencies. Furthermore, impedance match network 50 serves toimprove the transfer of RF power to plasma in plasma processing chamber10 by reducing the reflected power. Match network topologies (e.g.L-type, π-type, T-type, etc.) and automatic control methods are wellknown to those skilled in the art.

Vacuum pump system 30 can, for example, include a turbo-molecular vacuumpump (TMP) capable of a pumping speed up to 5000 liters per second (andgreater) and a gate valve for throttling the chamber pressure. Inconventional plasma processing devices utilized for dry plasma etch, a1000 to 3000 liter per second TMP is generally employed. TMPs are usefulfor low pressure processing, typically less than 50 mTorr. For highpressure processing (i.e., greater than 100 mTorr), a mechanical boosterpump and dry roughing pump can be used. Furthermore, a device formonitoring chamber pressure (not shown) can be coupled to the plasmaprocessing chamber 10. The pressure measuring device can be, forexample, a Type 628B Baratron absolute capacitance manometercommercially available from MKS Instruments, Inc. (Andover, Mass.).

Controller 14 includes a microprocessor, memory, and a digital I/O portcapable of generating control voltages sufficient to communicate andactivate inputs to plasma processing system 1 a as well as monitoroutputs from plasma processing system 1 a. Moreover, controller 14 canbe coupled to and can exchange information with RF generator 40,impedance match network 50, the gas injection system (not shown), vacuumpump system 30, the diagnostic system 12, as well as the backside gasdelivery system (not shown), the substrate/substrate holder temperaturemeasurement system (not shown), and/or the electrostatic clamping system(not shown). For example, a program stored in the memory can be utilizedto activate the inputs to the aforementioned components of plasmaprocessing system 1 a according to a process recipe in order to performan etching process, or an ashing process, or a treating process, or anycombination thereof. One example of controller 14 is a DELL PRECISIONWORKSTATION 610™, available from Dell Corporation, Austin, Tex.

Controller 14 can be locally located relative to the plasma processingsystem 1 a, or it can be remotely located relative to the plasmaprocessing system 1 a. For example, controller 14 can exchange data withplasma processing system 1 a using at least one of a direct connection,an intranet, and the internet. Controller 14 can be coupled to anintranet at, for example, a customer site (i.e., a device maker, etc.),or it can be coupled to an intranet at, for example, a vendor site(i.e., an equipment manufacturer). Additionally, for example, controller14 can be coupled to the internet. Furthermore, another computer (i.e.,controller, server, etc.) can, for example, access controller 14 toexchange data via at least one of a direct connection, an intranet, andthe internet.

The diagnostic system 12 can include an optical diagnostic subsystem(not shown). The optical diagnostic subsystem can include a detectorsuch as a (silicon) photodiode or a photomultiplier tube (PMT) formeasuring the light intensity emitted from the plasma. The diagnosticsystem 12 can further include an optical filter such as a narrow-bandinterference filter. In an alternate embodiment, the diagnostic system12 can include at least one of a line CCD (charge coupled device), a CID(charge injection device) array, and a light dispersing device such as agrating or a prism. Additionally, diagnostic system 12 can include amonochromator (e.g., grating/detector system) for measuring light at agiven wavelength, or a spectrometer (e.g., with a rotating grating) formeasuring the light spectrum such as, for example, the device describedin U.S. Pat. No. 5,888,337.

The diagnostic system 12 can include a high resolution Optical EmissionSpectroscopy (OES) sensor such as from Peak Sensor Systems, or VerityInstruments, Inc. Such an OES sensor has a broad spectrum that spans theultraviolet (UV), visible (VIS), and near infrared (NIR) lightspectrums. The resolution is approximately 1.4 Angstroms, that is, thesensor is capable of collecting 5550 wavelengths from 240 to 1000 nm.For example, the OES sensor can be equipped with high sensitivityminiature fiber optic UV-VIS-NIR spectrometers which are, in turn,integrated with 2048 pixel linear CCD arrays.

The spectrometers receive light transmitted through single and bundledoptical fibers, where the light output from the optical fibers isdispersed across the line CCD array using a fixed grating. Similar tothe configuration described above, light emitting through an opticalvacuum window is focused onto the input end of the optical fibers via aconvex spherical lens. Three spectrometers, each specifically tuned fora given spectral range (UV, VIS and NIR), form a sensor for a processchamber. Each spectrometer includes an independent A/D converter. Andlastly, depending upon the sensor utilization, a full emission spectrumcan be recorded every 0.1 to 1.0 seconds.

Furthermore, the diagnostic system 12 can include a system forperforming optical digital profilometry, such as the system offered byTimbre Technologies, Inc. (2953 Bunker Hill Lane, Suite 301, SantaClara, Calif. 95054).

In the embodiment shown in FIG. 7, a plasma processing system 1 b thatmay be used to implement the present invention can, for example, besimilar to the embodiment of FIG. 5 or 6 and further include either astationary, or mechanically or electrically rotating magnetic fieldsystem 60, in order to potentially increase plasma density and/orimprove plasma processing uniformity, in addition to those componentsdescribed with reference to FIG. 5 and FIG. 6. Moreover, controller 14can be coupled to magnetic field system 60 in order to regulate thespeed of rotation and field strength. The design and implementation of arotating magnetic field is well known to those skilled in the art.

In the embodiment shown in FIG. 8, a plasma processing system 1 c thatmay be used to implement the present invention can, for example, besimilar to the embodiment of FIG. 5 or FIG. 6, and can further includean upper electrode 70 to which RF power can be coupled from RF generator72 through impedance match network 74. A typical frequency for theapplication of RF power to the upper electrode can range from 0.1 MHz to200 MHz. Additionally, a typical frequency for the application of powerto the lower electrode can range from 0.1 MHz to 100 MHz. Moreover,controller 14 is coupled to RF generator 72 and impedance match network74 in order to control the application of RF power to upper electrode70. The design and implementation of an upper electrode is well known tothose skilled in the art.

In the embodiment shown in FIG. 9, a plasma processing system 1 d thatmay be used to implement the present invention can, for example, besimilar to the embodiments of FIGS. 5 and 6, and can further include aninductive coil 80 to which RF power is coupled via RF generator 82through impedance match network 84. RF power is inductively coupled frominductive coil 80 through dielectric window (not shown) to plasmaprocessing region 45. A typical frequency for the application of RFpower to the inductive coil 80 can range from 10 MHz to 100 MHz.Similarly, a typical frequency for the application of power to the chuckelectrode can range from 0.1 MHz to 100 MHz. In addition, a slottedFaraday shield (not shown) can be employed to reduce capacitive couplingbetween the inductive coil 80 and plasma. Moreover, controller 14 iscoupled to RF generator 82 and impedance match network 84 in order tocontrol the application of power to inductive coil 80. In an alternateembodiment, inductive coil 80 can be a “spiral” coil or “pancake” coilin communication with the plasma processing region 15 from above as in atransformer coupled plasma (TCP) reactor. The design and implementationof an inductively coupled plasma (ICP) source, or transformer coupledplasma (TCP) source, is well known to those skilled in the art.

Alternately, the plasma can be formed using electron cyclotron resonance(ECR). In yet another embodiment, the plasma is formed from thelaunching of a Helicon wave. In yet another embodiment, the plasma isformed from a propagating surface wave. Each plasma source describedabove is well known to those skilled in the art.

In general, the time to remove the layer of light-sensitive material canbe determined using design of experiment (DOE) techniques; however, itcan also be determined using endpoint detection. One possible method ofendpoint detection is to monitor a portion of the emitted light spectrumfrom the plasma region that indicates when a change in plasma chemistryoccurs due to substantially near completion of the removal of the layerof light-sensitive material from the substrate and contact with theunderlying material film. For example, portions of the spectrum thatindicate such changes include wavelengths of 482.5 nm (CO), and can bemeasured using optical emission spectroscopy (OES). After emissionlevels corresponding to those frequencies cross a specified threshold(e.g., drop to substantially zero or increase above a particular level),an endpoint can be considered to be complete. Other wavelengths thatprovide endpoint information can also be used. Furthermore, the ash timecan be extended to include a period of over-ash, wherein the over-ashperiod constitutes a fraction (i.e. 1 to 100%) of the time betweeninitiation of the ash process and the time associated with endpointdetection.

Additionally, the time for treating the hard mask to chemically alterthe surface layer of the hard mask can be determined by design ofexperiment (DOE) techniques, or monitoring the thickness of thechemically altered surface layer. The thickness of the chemicallyaltered surface layer can be determined using optical digitalprofilometry (ODP), as described above. After the thickness crosses aspecified threshold (e.g., increase to or above a particular level), anendpoint of the treatment process can be considered to be complete.Furthermore, the treatment time can be extended to include a period ofover-treatment, wherein the over-treatment period constitutes a fraction(i.e. 1 to 1000%) of the time between initiation of the treatmentprocess and the time associated with endpoint detection.

For example, as described above, a treatment process for removing alight-sensitive material and treating a hard mask can include exposingthe layers to an oxygen-containing plasma for 20 to 1400 seconds at asubstrate holder temperature ranging from 20 C to 400 C. For example, asubstrate with a hard mask having a thickness of approximately 1000 Åcan be exposed to an oxygen plasma for 60 seconds at a substrate holdertemperature of 250 C in order to remove the remaining layer oflight-sensitive material, followed by exposure to the oxygen plasma for120 seconds (i.e., 200% “over-treatment”) at a substrate holdertemperature of 250 C in order to form a chemically altered layer havinga thickness ranging from 10 Å to 1000 Å (i.e., fully oxidized).Additionally, for instance, if the substrate holder temperature isreduced (e.g., from 250 C), then the exposure time can be increased toaccommodate the slower process. Additionally, for example, thelight-sensitive material can be exposed to an oxygen-containing plasmafor 10 seconds to 200 seconds at a substrate holder temperature of 20 Cto 400 C, and the hard mask layer can be exposed to an oxygen-containingplasma for 10 seconds to 1200 seconds at a substrate holder temperatureof 20 C to 400 C.

Although embodiments have been presented for the treatment of a hardmask, such as a TERA coating, other hard mask materials can, in general,include organo-metallic compounds, or organo-silicon compounds.

Although only certain exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

1. A method of preparing a structure on a substrate comprising:preparing a film stack comprising a thin film, a hard mask formed onsaid thin film, and a layer of light-sensitive material formed on saidhardmask; forming a pattern in said layer of light-sensitive material;transferring said pattern to said hard mask; removing said layer oflight-sensitive material; treating said surface layer of said hard maskin order to modify said surface layer; and transferring said pattern tosaid thin film.
 2. The method of claim 1, wherein said preparingcomprises forming said hard mask comprising at least one of anorganosilicon layer and an organo-metallic layer.
 3. The method of claim1, wherein said preparing comprises forming said hard mask comprising atunable anti-reflective coating formed within said film stack having astructural formula R:C:H:X, wherein R is selected from the groupconsisting of Si, Ge, B, Sn, Fe, Ti, and combinations thereof, andwherein X is not present or is selected from the group consisting of oneor more of O, N, S, and F.
 4. The method of claim 1, wherein saidremoving said light-sensitive material comprises exposing saidlight-sensitive material to an oxygen-containing plasma.
 5. The methodof claim 1, wherein said treating said surface layer of said hard maskcomprises exposing said hard mask layer to an oxygen-containing plasma.6. The method claims 4, or 5, wherein said exposing said hard mask layerto said oxygen-containing plasma comprises exposing said hard mask layerto a plasma formed from the introduction of oxygen (O₂).
 7. The methodof claim 1, wherein said removing said light-sensitive layer and saidtreating said surface layer of said hard mask are performedconcurrently.
 8. The method of claim 1, further comprising: determiningan endpoint for completion of said removing said layer oflight-sensitive material.
 9. The method of claim 1, further comprising:determining an endpoint for completion of said treating said surfacelayer of said hard mask.
 10. A chemically altered hard mask comprising:a hard mask layer; and a chemically altered surface layer of said hardmask layer.
 11. The chemically altered hard mask of claim 10, whereinsaid hard mask layer comprises an organosilicate layer.
 12. Thechemically altered hard mask of claim 10, wherein said hard mask layercomprises a tunable anti-reflective coating having a structural formulaR:C:H:X, wherein R is selected from the group consisting of Si, Ge, B,Sn, Fe, Ti, and combinations thereof, and wherein X is not present or isselected from the group consisting of one or more of O, N, S, and F. 13.The chemically altered hard mask of claim 10, wherein said chemicallyaltered surface layer comprises an oxidized hard mask surface layer. 14.A plasma processing system for treating a hard mask used for etching afeature in a thin film on a substrate comprising: a process chamber; asubstrate holder coupled to said process chamber and configured tosupport said substrate; means for introducing a treating gas; means forforming a plasma; and a controller coupled to said means for introducingsaid treating gas and said means for forming said plasma, and configuredto execute a process recipe utilizing said plasma to chemically alterthe surface layer of said hard mask.
 15. The system of claim 14, whereinsaid treating gas comprises oxygen (O₂).
 16. The system of claim 14,further comprising: means for introducing an etching gas.
 17. The systemof claim 14, further comprising: means for introducing an ashing gas.18. The system of claim 14, further comprising: a diagnostic systemcoupled to said process chamber and said controller, and configured todetermine an endpoint of said utilizing said plasma to chemically alterthe surface layer of said hard mask.
 19. The system of claim 18, whereinsaid diagnostic system comprises an optical digital profilometry (ODP)system.
 20. The system of claim 18, wherein said diagnostic systemfurther comprises an optical emission spectroscopy (OES) system fordetecting an endpoint of at least one of an etching process, and anashing process.
 21. The method of claim 4, wherein said exposing saidlight-sensitive material to said oxygen-containing plasma includessetting an exposure time and a substrate holder temperature for saidexposure.
 22. The method of claim 21, wherein said setting said exposuretime includes setting said exposure time for approximately 10 seconds toapproximately 200 seconds.
 23. The method of claim 21, wherein saidsetting said substrate holder temperature includes setting saidsubstrate holder temperature at approximately 20 C to 400 C.
 24. Themethod of claim 5, wherein said exposing said hard mask layer to saidoxygen-containing plasma includes setting an exposure time and asubstrate holder temperature for said exposure.
 25. The method of claim24, wherein said setting said exposure time includes setting saidexposure time for approximately 10 seconds to approximately 1200seconds.
 26. The method of claim 24, wherein said setting said substrateholder temperature includes setting said substrate holder temperature atapproximately 20 C to 400 C.
 27. The method of claim 1, wherein saidremoving said light-sensitive material is followed by said treating saidsurface layer of said hard mask, said exposing and said treatingcomprise exposing said substrate to an oxygen-containing plasma for anexposure time at a substrate holder temperature.
 28. The method of claim27, wherein said exposing said substrate to said oxygen-containingplasma for said exposure time at said substrate holder temperatureincludes exposing said substrate for said exposure time ranging fromapproximately 20 seconds to 1400 seconds, at said substrate holdertemperature ranging from approximately 20 C to 400 C.